As is well known to those versed in the venetian blind art, conventional metal blind slats are subject to certain problems in manufacture, one of which is called bow. In particular, the metal slats are necessarily slightly crowned or transversely arcuate in order to be self-sustaining in their horizontal position between widely spaced ladders. In the trade the term negative bow refers to a crowned slat having its convexly crowned surface longitudinally arcuately concave or bowed. Conversely, positive bow refers to a crowned slat strip having its convex crown surface longitudinally convexly curved.
Heretofore, it has been extremely difficult to avoid, eliminate or minimize bow, prior bow control methods and apparatus being slow, inaccurate and requiring considerable machine down time, without assurance of continued satisfactory slat production.